Method of vibratory grinding and apparatus therefor



y 9, 1961 w. PODMORE, JR, ETAL 2,983,454

METHOD OF VIBRATORY GRINDING AND APPARATUS THEREFOR Filed Jan. 7, 1959 Inventors WILLIAM PODM RE JR. HENRY L. PODMORE ttorney i METHOD OF VIBRATORY GRINDING AND 4 Claims. (Cl. 24130) This invention relates to grinding mills, which term is intended to include both batch mills and mills for continuous grinding.

The invention can be applied to mills for the size reduction of all types of material, including the pulverisation of fine materials.

The invention is concerned with mills in which the grinding action is produced by means of a vibratory or agitating movement applied to a pan or container for the material to be processed, as distinct from mills in which the container is continuously rotated about its axis.

In these known mills the grinding action is usually produced by having a number of balls or the like in he pan or container. The balls may be of steel, stone, porcelain or other material. The grinding media however varies in accordance with the characteristics of the materials being processed and this invention is not restricted to any particular kind of grinding media.

A difficulty which is commonly experienced in these mills is that the motion which is imparted to the pan or container tends to consolidate the charge (that is to say, the material being ground and the grinding media itself). As a result the grinding media b'ecomes blocked and the grinding action is reduced. This difliculty is experienced both with vibratory mills and rotating mills.

In existing vibratory mills the motion is in the form of an oscillating movement in a horizontal plane. It is usually a slow movement of a fairly large amplitude and it moves the charge to and fro against the walls of the container. It gives rise to considerable wear on the grinding media, which in turn causes contamination of the product. The grinding action is rather slow, and it is diflicult to grind down to fine particles in such mills. They also require considerable power input for their operation.

According to the present invention the pan or container of a grinding mill is flexibly mounted and has connected to it means serving to impart to it a high frequency rotational or gyrating vibration about an approximately vertical axis with an upward and downward component in the rotational movement.

By this arrangement a motion can be imparted to the charge which is barely perceptible but which tends in general to circulate the charge around the container and avoids the tendency for the charge tosettle. The grinding action is, however, increased. The higher frequency gives a higher output of the product in relation to the power input, and using a given frequency a much larger mill can be employed than would be the case with the conventional oscillatory vibration already referred to.

A constructional form of the invention will now be described with reference to the accompanying drawings in which:

Figure l is a sectional elevation through a grinding mill.

U ita States e c Patented May 9, 1961 gure 1. g

The mill'consistsof a cylindrical or other pan 10 which may be made of rubber or similar slightlylflexible materialtfitted within a steel or other shellll. The shell receives and enclosesa bottom plate 12. This pan unit, 10,11,12 is mounted upona number of springs. As shown there are threespringslli, arranged 120 apart. Theirnature' may vary; as shown they are leaf springs but coil or other types might be employed. The springs 13 are mounted in an inclined position. Their lower ends are anchored to a base 14. Their upper ends are attached to .the plate 12, so that the pan unit is supported on the upper ends of the springs. These springs are grouped circumferentially around a vibrator unit which is shown as of the electromagnetic type comprising a magnet 15, coil 16 and armature 17, supported on lugs 18 upstanding fromthe base 14. The springs and vibrator unit are enclosed within a housing 19 attached to the base. The grinding media in the pan is shown as a number of balls 20.

It will be seen by this arrangement the pan is supported upon the inclined springs which extend upwards from the base cantilever-fashion, and the vibration created by the unit 15, 16, 17 will therefore be communicated to the pan. The unit 15, 16, 17 is centrally arranged with reference to the vertical axis of the pan 10. A rapid succession of small to and fro rotary movements of a somewhat spiral character, will therefore be set up. Because the movements are so slight there will be little wear on the balls or the like and consequentially little or no contamination of the product, while finer grinding can be achieved. The movement may be sufiiciently small as to be less than the mean diameter of the units of grinding media.

The invention is not restricted to an electromagnetic type of vibrator. The movement can be obtained in any other convenient way. For example in a large mill it might be convenient to have an out-of-balance mass such as a weighted fly-wheel to which the necessary rotary movement is imparted. Hydraulic or pneumatic vibrators are also available and could be applied to the purpose.

What we claim is:

1. A grinding mill comprising a container adapted to receive material to be ground, a plurality of unsecured grinding media contained therein, means flexibly supporting said container, and means for imparting high frequency vibration thereto about a substantially vertical axis, said vibration having a vertical component and a rotational component.

2. A grinding mill comprising a container adapted to receive material to be ground, a plurality of unsecured grinding media contained therein, and means for imparting a high frequency vibratory motion of small amplitude, having a vertical component and a gyrating motion in a substantially horizontal plane, whereby said grinding media and material to be ground circulates in said container as said media grinds said material.

3. A grinding mill comprising a container, a charge of grinding media and material to be ground, means for vibrating said container, media and charge at high frequency and with an amplitude less than the mean diameter of the grinding units, the vibration having a rota- Figure 2 is a sectional plan on the line n-nbr Fig- 3 the units of grinding media, said vibrations having a vertical component and a rotational component, whereby said media and material to be ground circulate around and about a vertical 'axis.

References Cited in the fileof this patent A UNITED STATES PATENTS 'Conradi Sept. 29, 1942 4 Lentz Mar. 3, 1953 Stone Dec. 20, 1955 FOREIGN PATENTS Great Britain 1910 Germany June 16, 1893 Sweden Nov. 13, 1941 Austria July 10, 1934 Switzerland Feb. 1, 1936 Germany Apr. 1, 1911 Great Britain Aug. 31, 1945 France July 15, 1957 

